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// Imported from
// https://github.com/ros/ros_comm/blob/a2ca01ecf31d677dd5c1b08cc6852bd0dac02b97/clients/roscpp/include/ros/parameter_adapter.h

#ifndef MESSAGE_FILTERS__PARAMETER_ADAPTER_HPP_
#define MESSAGE_FILTERS__PARAMETER_ADAPTER_HPP_

#include <memory>
#include <type_traits>

#include "message_filters/message_event.hpp"

namespace message_filters
{

/**
 * \brief Generally not for outside use.  Adapts a function parameter type into the message type, event type and parameter.  Allows you to
 * retrieve a parameter type from an event type.
 *
 * ParameterAdapter is generally only useful for outside use when implementing things that require message callbacks
 * (such as the message_filters package)and you would like to support all the rclcpp message parameter types
 *
 * The ParameterAdapter is templated on the callback parameter type (\b not the bare message type), and provides 3 things:
 *  - Message typedef, which provides the bare message type, no const or reference qualifiers
 *  - Event typedef, which provides the message_filters::MessageEvent type
 *  - Parameter typedef, which provides the actual parameter type (may be slightly different from M)
 *  - static getParameter(event) function, which returns a parameter type given the event
 *  - static bool is_const informs you whether or not the parameter type is a const message
 *
 *  ParameterAdapter is specialized to allow callbacks of any of the forms:
\verbatim
void callback(const std::shared_ptr<M const> &);
void callback(const std::shared_ptr<M> &);
void callback(std::shared_ptr<M const>);
void callback(std::shared_ptr<M>);
void callback(const M &);
void callback(M);
void callback(const MessageEvent<M const> &);
void callback(const MessageEvent<M> &);
\endverbatim
 */
template<typename M>
struct ParameterAdapter
{
  typedef typename std::remove_reference<typename std::remove_const<M>::type>::type Message;
  typedef MessageEvent<Message const> Event;
  typedef M Parameter;
  static const bool is_const = true;

  static Parameter getParameter(const Event & event)
  {
    return *event.getMessage();
  }
};

template<typename M>
struct ParameterAdapter<const std::shared_ptr<M const> &>
{
  typedef typename std::remove_reference<typename std::remove_const<M>::type>::type Message;
  typedef MessageEvent<Message const> Event;
  typedef const std::shared_ptr<Message const> Parameter;
  static const bool is_const = true;

  static Parameter getParameter(const Event & event)
  {
    return event.getMessage();
  }
};

template<typename M>
struct ParameterAdapter<const std::shared_ptr<M> &>
{
  typedef typename std::remove_reference<typename std::remove_const<M>::type>::type Message;
  typedef MessageEvent<Message const> Event;
  typedef std::shared_ptr<Message> Parameter;
  static const bool is_const = false;

  static Parameter getParameter(const Event & event)
  {
    return MessageEvent<Message>(event).getMessage();
  }
};

template<typename M>
struct ParameterAdapter<const M &>
{
  typedef typename std::remove_reference<typename std::remove_const<M>::type>::type Message;
  typedef MessageEvent<Message const> Event;
  typedef const M & Parameter;
  static const bool is_const = true;

  static Parameter getParameter(const Event & event)
  {
    return *event.getMessage();
  }
};

template<typename M>
struct ParameterAdapter<std::shared_ptr<M const>>
{
  typedef typename std::remove_reference<typename std::remove_const<M>::type>::type Message;
  typedef MessageEvent<Message const> Event;
  typedef std::shared_ptr<Message const> Parameter;
  static const bool is_const = true;

  static Parameter getParameter(const Event & event)
  {
    return event.getMessage();
  }
};

template<typename M>
struct ParameterAdapter<std::shared_ptr<M>>
{
  typedef typename std::remove_reference<typename std::remove_const<M>::type>::type Message;
  typedef MessageEvent<Message const> Event;
  typedef std::shared_ptr<Message> Parameter;
  static const bool is_const = false;

  static Parameter getParameter(const Event & event)
  {
    return MessageEvent<Message>(event).getMessage();
  }
};

template<typename M>
struct ParameterAdapter<const MessageEvent<M const> &>
{
  typedef typename std::remove_reference<typename std::remove_const<M>::type>::type Message;
  typedef MessageEvent<Message const> Event;
  typedef const MessageEvent<Message const> & Parameter;
  static const bool is_const = true;

  static Parameter getParameter(const Event & event)
  {
    return event;
  }
};

template<typename M>
struct ParameterAdapter<const MessageEvent<M> &>
{
  typedef typename std::remove_reference<typename std::remove_const<M>::type>::type Message;
  typedef MessageEvent<Message const> Event;
  typedef MessageEvent<Message> Parameter;
  static const bool is_const = false;

  static Parameter getParameter(const Event & event)
  {
    return MessageEvent<Message>(event);
  }
};

}  // namespace message_filters

#endif  // MESSAGE_FILTERS__PARAMETER_ADAPTER_HPP_
